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Onyesi-john.abiagam@stud.hshl.de (Diskussion | Beiträge)
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Onyesi-john.abiagam@stud.hshl.de (Diskussion | Beiträge)
wiki-autoren
37 Bearbeitungen
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== Working principle ==
== Working principle ==


The working principle describes how the DMS load cell and the HX711AD convert an applied force into a digital signal.
This section explains how the DMS load cell and the HX711AD convert an applied force into a digital signal.


=== DMS Load Cell ===
=== DMS Load Cell ===
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==== Introduction ====
==== Introduction ====


A DMS load cell is a force transducer that converts mechanical force into an electrical signal. It consists of a deformable metal body with strain gauges attached to its surface.
A DMS load cell converts mechanical force into an electrical signal. It consists of:
* a deformable metal body
* strain gauges attached to the surface
* resistance changes when stretched or compressed 


[[Datei:Weight image.jpeg|thumb|mini|400px|Figure 1: Structure of the weight scale]]
[[Datei:Load cell2.png|center|350px|Figure 1: Structure and deformation of a load cell. Source: https://learn.sparkfun.com/tutorials/getting-started-with-load-cells]]
[[Datei:Load cell2.png|thumb|mini|400px|Figure 2: Structure and deformation of a load cell. Source: https://learn.sparkfun.com/tutorials/getting-started-with-load-cells]]


Figure 1 shows the structure of a load cell and its deformation under load. The strain gauges detect small deformations and convert them into changes in electrical resistance.
<div style="clear: both;"></div>


==== Working Principle ====
==== Working Principle ====


The operation of the load cell follows these steps:
When force is applied:
* the metal body deforms 
* strain gauges change resistance 
* gauges are wired in a Wheatstone bridge 
* deformation → bridge becomes unbalanced 
* output: small differential voltage 


* A force is applied to the load cell 
[[Datei:Full Wheatstone Bridge.png|center|300px|Figure 2: Wheatstone bridge configuration. Source: https://learn.sparkfun.com/tutorials/getting-started-with-load-cells]]
* The metal body undergoes elastic deformation 
* The strain gauges are:
** stretched: resistance increases 
** compressed: resistance decreases 
* The strain gauges are arranged in a Wheatstone bridge


[[Datei:Full Wheatstone Bridge.png|mini|Figure 3: Wheatstone bridge configuration. Source: https://learn.sparkfun.com/tutorials/getting-started-with-load-cells]]
<div style="clear: both;"></div>
[[Datei:Load cell wiring.png|mini|Figure 4: Loadcell Wheatstone bridge configuration. Source: https://learn.sparkfun.com/tutorials/getting-started-with-load-cells]]
 
 
Figure 2 shows the Wheatstone bridge configuration used in the load cell.
 
* In the unloaded state:
** the bridge is balanced 
** output voltage is zero 
* When a load is applied:
** the bridge becomes unbalanced 
** a small differential voltage is generated 


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==== Introduction ====
==== Introduction ====


The HX711AD is a measuring amplifier designed to process the small output signal from a load cell. It combines signal amplification and analog-to-digital conversion in a single device.
The HX711AD processes the small differential signal from the load cell.
 
It includes:
[[Datei:HX711 Module.png|thumb|mini|400px|Figure 5: HX711 module and pin configuration. Source: https://justdoelectronics.com/load-cell-hx711-module/]]
* a programmable gain amplifier (PGA) 
* a 24‑bit sigma‑delta ADC 


Figure 5 shows the HX711 module and its pin configuration.
[[Datei:HX711 Module.png|center|350px|Figure 3: HX711 module and pin configuration. Source: https://justdoelectronics.com/load-cell-hx711-module/]]


<div style="clear: both;"></div>


==== Working Principle ====
==== Working Principle ====


The HX711 processes the signal from the load cell as follows:
Signal processing steps:
* load cell outputs a millivolt‑level differential signal (A+, A−) 
* PGA amplifies the signal
* 24‑bit ADC converts it to digital 
* microcontroller reads data via:
** DOUT (data) 
** SCK (clock) 


[[Datei:Internal HX711.png|thumb|mini|400px|Figure 6: Internal structure of HX711]]
[[Datei:Block Internal Hx711.png|center|350px|Figure 4: Source: https://cdn.sparkfun.com/datasheets/Sensors/ForceFlex/hx711_english.pdf


Figure 6 shows the internal structure of the HX711.
[[Datei:Block Internal Hx711.png|mini]]
]]


* The load cell provides a differential voltage signal (A+ and A−) 
<div style="clear: both;"></div>
* The signal is very small (millivolt range) 
* The internal amplifier (PGA) amplifies the signal 
* The amplified signal is converted using a 24-bit sigma-delta ADC 
* The output is a digital value proportional to the applied force 
* The data is transmitted to the microcontroller via:
** DOUT (data) 
** SCK (clock)


= Technical Overview =
= Technical Overview =

Version vom 25. März 2026, 23:29 Uhr

fig. 1: DMS load cell with measuring amplifier HX711AD
Autor: Onyesi John Abiagam
Sprache: DE EN

Introduction

Requirements

Table 1: Requirements for the Unit
Req. Description Priority
1 The mass must be determined using the HX711AD load cell via Arduino and Simulink. 1
2 The measuring range must be determined. 1
3 The measurement uncertainty (1σ) must be determined for the measuring range and displayed as a confidence interval. 2
4 The on/off button starts the system. The sensor must first be calibrated and display 0 g. 1
5 The weight must be referenced for the measuring range. 1
6 The measured values ​​must be filtered/smoothed over time. 1
7 A beep must indicate when the measured value is stable/constant. 1
8 The sensor system must display the weight in g on a display. 1
9 The tara button resets the current weight to 0 g (recalibration). 1

Working principle

This section explains how the DMS load cell and the HX711AD convert an applied force into a digital signal.

DMS Load Cell

Introduction

A DMS load cell converts mechanical force into an electrical signal. It consists of:

  • a deformable metal body
  • strain gauges attached to the surface
  • resistance changes when stretched or compressed
Figure 1: Structure and deformation of a load cell. Source: https://learn.sparkfun.com/tutorials/getting-started-with-load-cells
Figure 1: Structure and deformation of a load cell. Source: https://learn.sparkfun.com/tutorials/getting-started-with-load-cells

Working Principle

When force is applied:

  • the metal body deforms
  • strain gauges change resistance
  • gauges are wired in a Wheatstone bridge
  • deformation → bridge becomes unbalanced
  • output: small differential voltage
Figure 2: Wheatstone bridge configuration. Source: https://learn.sparkfun.com/tutorials/getting-started-with-load-cells
Figure 2: Wheatstone bridge configuration. Source: https://learn.sparkfun.com/tutorials/getting-started-with-load-cells

---

HX711AD Measuring Amplifier

Introduction

The HX711AD processes the small differential signal from the load cell. It includes:

  • a programmable gain amplifier (PGA)
  • a 24‑bit sigma‑delta ADC
Figure 3: HX711 module and pin configuration. Source: https://justdoelectronics.com/load-cell-hx711-module/
Figure 3: HX711 module and pin configuration. Source: https://justdoelectronics.com/load-cell-hx711-module/

Working Principle

Signal processing steps:

  • load cell outputs a millivolt‑level differential signal (A+, A−)
  • PGA amplifies the signal
  • 24‑bit ADC converts it to digital
  • microcontroller reads data via:
    • DOUT (data)
    • SCK (clock)
Figure 4: Source: https://cdn.sparkfun.com/datasheets/Sensors/ForceFlex/hx711_english.pdf
Figure 4: Source: https://cdn.sparkfun.com/datasheets/Sensors/ForceFlex/hx711_english.pdf

Technical Overview

Pin Assignment

Measurement method

Measuring Circuit

Software

Arduino IDE

Simulink

Measurement

Video

Datasheets

Related Links

SVN-Repository

https://svn.hshl.de/svn/HSHL_Projekte/trunk/Arduino_Sensorsammlung


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